August 22, 2019

Medical Update

New Treatments and Challenges of Acute Stroke Care

Pankajavalli Ramakrishnan, MD, PhD

Advancements in stroke care are moving fast, leading to better outcomes for patients and new challenges for healthcare providers.

“Just 5 to 10 years ago is like a different era in stroke treatment,” says Pankajavalli Ramakrishnan, MD, PhD, a neurointerventionalist at Riverside Health System. “There are stark differences in the way that things were treated then and how we care for them now.”

tPA for Small Artery Occlusions
The changes in stroke care began in 1995, when the first trials for intravenous tissue plasminogen activator (tPA) began. These trials showed the treatment could reduce some disability for patients who experienced a stroke.

“Over the next 20-some years, tPA was slowly adopted as the standard for dissolving clots,” says John Baker, MD, PhD, a neurointerventionalist at Chesapeake Regional Healthcare. “Unfortunately, that medication only opens the artery about 30 percent of the time, and only about 50 percent of patients treated with tPA improve.”

John Baker, MD, PhD

While tPA could assist with smaller clots by restoring blood flow and minimizing damage, it has become clear that it is no match for large artery occlusions.

“We needed to have a physical way to remove the larger blood clot and restore blood flow in a timely manner, so you can save the bulk of the brain that would have otherwise died,” says Dr. Ramakrishnan. 

Mechanical Thrombectomy for Large Artery Occlusions
Almost as long as tPA has been around, interventionists have been striving to create devices that would allow the removal of large blood clots from the brain. They began working with engineers to perfect devices that allowed for fast, minimally invasive stroke treatment. Early first-generation devices didn’t always achieve clinically observable results.

“In 2015, overwhelming evidence from studies around the world showed that the second-generation devices were highly successful in opening blood vessels by removing the larger blood clots,” says Dr. Ramakrishnan. “They also clinically made an impact for minimizing permanent disability.”

Neurointerventional surgeons can now use multiple techniques to remove blood clots from the brain. Aspiration thrombectomy uses a catheter and suction to pull out the clot, leading to immediate recanalization. 

Stent retriever thrombectomy deploys a stent through the blood clot, entrapping it. Once the stent surrounds the clot, neurointerventionalists remove both the clot and stent together. 

Surgeons may also use a combination of the two techniques to achieve the best outcomes. So far, studies suggest that both techniques are equally effective in reducing disability.

Initial guidelines for mechanical thrombectomy recommended its use for patients who were seen within 6 hours of their last known well. This window of opportunity was viewed as the time when thrombectomy would have the largest benefit.

“That’s like saying that two people who are the same height and weight can run the same distance in the same timeframe,” says Dr. Ramakrishnan. “However, no two brains have the same ability to withstand the same extent of absence of blood flow. In the past, time was used as a measure of likely viable brain that could still be salvaged by opening up blocked arteries. Now, we can use better techniques in determining the extent of viable brain, rather than using time lapsed without blood flow as a surrogate for salvageable brain.”

Expanding Mechanical Thrombectomy Care with Imaging Technology
Two randomized-controlled trials, called DEFUSE 3 and DAWN, began to look at using thrombectomy for patients who fell outside the six-hour window with a large artery occlusion in the anterior portion of the brain. These studies showed that some patients had a significant mismatch between already infarcted brain and brain that could still be salvaged, suggesting that much larger portions of the brain could be saved even outside of the six-hour window.

Both studies were halted early, as analyses revealed an overwhelmingly large benefit to patients experiencing such a stroke.

“We’ve found that going up into that artery to take out the clot, even all the way out to 24 hours from last known well, can lead to good patient outcomes,” says Dr. Baker. “Because of advances in mechanical thrombectomy, we can get the artery open about 90 percent of the time, with 50 percent of patients doing better.”

New Challenges to Improve Treatment Times
While mechanical thrombectomy is beneficial to many stroke patients, it requires expertise and equipment that may not be widely available. In Hampton Roads, mechanical thrombectomy is available at Chesapeake Regional Medical Center, Riverside Regional Medical Center, and Sentara Norfolk General Hospital. 

“That leaves large portions of our community without a hospital that offers this particular service,” says Dr. Baker. “Those patients would go to the nearest hospital to be evaluated, potentially receive IV meds, then get transported to another hospital to have the procedure. That results in time delays, so we need to determine how to offer treatment to more people, more quickly.” 

Strokes present unique challenges because they require fast care and fast imaging services. It can be difficult to identify a stroke in the field, let alone to know if the stroke is occurring in a small or large artery.

The Virginia Stroke System Task Force is working to map out the state and develop strategies to deliver care more quickly, such as diverting patients to more advanced stroke centers. In some densely populated areas of the country, teams like Dr. Baker’s can go to the patient instead of the other way around. 

“If the person is at a local hospital, the anesthesia and hospital team can get those patients ready for thrombectomy,” says Dr. Baker. “It may save time by bringing the neurointerventional team to the patient instead of sending the patient on a long ride in an ambulance.” 

This paradigm does pose some challenges. It requires hospitals to have the necessary infrastructure, including equipment and personnel, in place. It also can leave gaps in coverage as the treatment team travels to other hospitals. 

In many parts of the country, stroke care is evolving around centralization of expertise, such as for trauma. Two years ago, the Peninsulas EMS Region developed its own protocols similar to those for triaging trauma patients. EMS uses severity measures, such as number of stroke symptoms, to determine if a patient may be more likely to have a large artery occlusion. If the patient’s travel time doesn’t increase by more than 15 minutes, the patient is taken to Riverside Regional Medical Center for care first instead of traveling to the nearest hospital. 

“The results that we have so far show that people who are eligible for IV tPA still get it, but patients who benefit from thrombectomy are getting it faster and having less disability,” says Dr. Ramakrishnan. “The efforts started by our partnership with Peninsulas EMS have been recognized by the Virginia Stroke System Task Force and the Department of Health.”

Other EMS regions are beginning to emulate the Peninsulas’ efforts, working to train their EMS in the new stroke assessments.

Despite challenges in delivering care, both Dr. Baker and Dr. Ramakrishnan agree that stroke care has vastly improved and believe it will continue to improve.

“It’s an exciting time in comparison to when I first started,” says Dr. Baker. “Back then, we could only watch what happened as the brain died. It’s been wonderful to follow the progression of treatment in the last 25 years.”

“It’s the best time to do what we do in caring for stroke patients,” says Dr. Ramakrishnan. “They’ve never had more options than they have now; it’s just a matter of getting them to the right place as quickly as possible.”